Police in Colombia have uncovered a submarine, which they believe was built by drug smugglers to transport cocaine.

The nearly complete eight-metre fibreglass vessel, capable of carrying 10 tonnes of the drug, worth $200m, was found in the Pacific port of Tumaco.

Police had been monitoring its construction for six months.

They believe the Norte del Valle cartel, the last surviving Colombian drug trafficking organisation, planned to use it to smuggle drugs to the US.

Colombia's Department of Administrative Security says the submarine would have been used to evade radar and naval patrol ships, taking drugs out to sea where they could be transferred to high-speed motorboats for the journey to Central America and on to the United States.

"The ingenuity of drug traffickers is amazing. They will seek any way to avoid the coast guard," Eduardo Fernandez, head of Colombia's secret police in Valle del Cauca state, told the Associated Press.

The submarine was apparently designed to be ready for Easter, when the smugglers believed police would be less vigilant.

"On the contrary, security in the area has been boosted," said Mr Fernandez.

No arrests were made in Friday's operation.

In 2000, police found a 30-metre steel submarine under construction far inland, near the capital Bogota It would have been capable of carrying up to 200 tonnes of cocaine.